In a medical procedure, during which a patient is sedated or under anesthesia, it is important that the patient's airway and the delivery of gases are monitored closely. There are two main types of anesthesia utilized in caring for patients under anesthesia, namely Monitored Anesthetic Care (MAC) and General Anesthesia (GA). The basic description of “monitoring the airway” is really an oversimplified description of capnography, which is the monitoring of the concentration of end tidal carbon dioxide (“ETCO2”) or exhaled carbon dioxide (“CO2”) of a patient in order to assess the physiological status and/or determine the adequacy of ventilation during anesthesia.
In the MAC method of capnography, the airway of a patient may be monitored while the patient is wearing a nasal cannula or a simple face mask via which a gas, such as oxygen, is administered to the patient. The face mask may be a plastic, possibly a clear plastic that covers the nose and mouth and is secured to the face by an elastic band around the back of the head. The nasal cannula may be inserted into the nares so that the outflow of oxygen, for example, is inhaled by the patient through the nose.
Alternatively, in GA methods, anesthesia may be accomplished without a nasal cannula or face mask, but instead with a breathing circuit that connects the patient to an anesthetic machine and ventilator. This may be accomplished via an inspiratory and expiratory limb of the breathing circuit connected to the patient at a breathing device that terminates at or about the tracheal opening of the patient's lungs.
In some instances, the effects of sedatives, narcotics, and the majority of general anesthetics decrease respiratory drive and can cause brief or prolonged periods of apnea. Because of such a situation, the implementation of capnography increases the margin of safety for delivery of anesthesia.